1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing electronic parts, each of which comprises a lead frame and an electronic element, for example, a quartz resonator mounted thereon, and each being entirely molded using a sealing resin. More particularly, the present invention relates to the bending of leads of the electronic part in the manufacture thereof.
2. Background Art
FIGS. 6A and 6B are a perspective view of a quartz oscillator and an explanatory drawing of leads of the quartz oscillator respectively. The quartz oscillator 1 comprises a resin mold section 2 with a built-in electronic element and leads 3 projecting therefrom. The resin mold section 2 has recesses 2a formed in a bottom portion thereof for housing tip sides of the leads 3. The leads 3 are bent toward the bottom portion in such a manner as to enclose a side of the resin mold section 2, and have their tip portions housed in the recesses 2a. By folding the leads 3 toward the bottom portion of the resin mold section 2 in the above manner, the height H of the quartz oscillator 1, including the resin mold section 2 and the leads 3, is reduced to lessen the thickness and size of the quartz oscillator. The leads 3 are molded by means of three bending operations using progressive press dies.
FIG. 7 shows how the leads are bent during each bending operation. The letter xe2x80x9caxe2x80x9d denotes a state prior to bending, and xe2x80x9cbxe2x80x9d shows that the first bending operation has bent a root portion of each of the leads 3 upward while bending a tip portion thereof downward. The letter xe2x80x9ccxe2x80x9d shows that the second bending operation has bent the root portion downward. Finally, the third bending operation bends the tip portion of the lead 3 toward the bottom portion to form it as shown in FIG. 6B.
FIG. 8 shows a pressing section (stage) for a second bending operation. This second bending stage comprises a die 11, a stripper plate 12, and a punch 13. The press bending operation is carried out by lowering the punch 13 while the leads 3 of the quartz oscillator 1 placed on the die 11 are fixedly pressed on the die 11 by means of the stripper plate 12.
In the second bending stage, a space at which the leads 3 are pressed between the stripper plate 12 and the die 11 (identified by xe2x80x9cdxe2x80x9d in the drawings) is small, thereby preventing the product from being sufficiently fixed. Thus, although the base portion of the lead 3 must be bent at an edge position of the die 11, the lead 3 is actually bent at a root thereof with respect to the resin mold section 2. If the third bending operation is performed in this state, a crevice C occurs in the root of the lead 3 with respect to the resin mold section 2 as shown in FIG. 9. In addition, if the lead is bent at the root in this manner, the height H of the entire quartz oscillator 1 increases and fails to meet a required quality.
FIG. 10 shows a pressing section (stage) for a third bending operation. The third bending stage employs a cam mechanism for avoiding spring back of the leads 3. The cam mechanism comprises cam drivers 21 provided on a punch plate side and cam levers 22 rotatably supported and provided on a die plate side. When the cam drivers 21 are lowered, tips of the cam drivers 21 engage with the cam levers 22 to rotationally move the cam levers 22 inward to bend the leads 3 inward.
The cam mechanism of the above described third bending stage avoids the spring back of the leads 3 but creates the following problems when electronic parts are mass-produced:
(1) The shapes of parts of the cam mechanism are so complicated that maintenance operations cannot be easily performed. The shapes of the cam levers 22 and the lever holders 23 are complicated, and in particular, the cam lever 22 cannot be easily shaped, so that fine adjustments are often required during replacement of these parts.
(2) Cam lever shafts 25 are thin (they are forced to be thin due to mechanical restraints) and weak. Further the shafts 25 are easily worn away because the shaft move freely and the cam levers 22 have a narrow and fixed rotational movement range. When the cam lever shafts 25 are worn away, the cam levers 22 may shift from their correct positions, resulting in inappropriate bending.
(3) The cam mechanism (the cam levers) is located on a lower die set side, so that scraps from the resin mold (package) fall into and interfere with the cam mechanism to affect bending accuracy. For example, scraps may be caught in the cam mechanism and may not fall further downward, so that one of the cam levers 22 is stopped at the position shown in the right of FIG. 10 and is prevented from rotational movement. Alternatively, if a large scrap is present in a portion A in FIG. 10, the corresponding cam lever 22 cannot be rotationally moved to a final position, thereby preventing the lead 3 from being bent to a predetermined position. The resin mold in this state is fed to the next step, where problems occur that the parts may be destroyed or the dies may be damaged.
It is an object of the present invention to provide a method and apparatus for manufacturing electronic parts so as to allow their leads to be accurately bent.
It is another object of the present invention to provide the method and apparatus for manufacturing electronic parts to enable easy maintenance operations.
In a method for manufacturing at least one electronic part according to one aspect of the present invention, each electronic part includes a resin mold section with a built-in electronic element and leads projecting therefrom. The method comprises a first step of forming a V-shaped groove near a root of each of the leads and a second step of pressing a tip side of each lead to bend that lead downward near the V-shaped groove. According to the present invention, since the V-shaped groove is formed near the root of each lead during the first step, a bending position for the second step is set at the position of the V-shaped groove, thereby enabling bending at an appropriate position. In addition, a tip side of the lead is pressed during the second step, so that stress exerted on the root of the lead can be lessened to prevent occurrence of a crevice.
According to another aspect of the invention, the V-shaped groove is formed to have a depth between about one-third and about one-half of a board thickness of the lead. The strength of the recess in the lead is thus retained.
According to another aspect of the invention, in the second step, the lead is bent so as not to close the V-shaped groove. Since the lead is bent at the second step so as not to close the V-shaped groove, a bending portion is set at the position of the V-shaped groove during subsequent bending steps, thereby enabling bending at an appropriate position.
In a method for manufacturing at least one electronic part according to another aspect of the present invention, each electronic part includes a resin mold section with a built-in electronic element and leads projecting therefrom. The method comprises a first step of bending a first portion of each lead to form a first bent portion, a second step of bending a second portion, which is different from the first portion, of each lead to form a second bent portion, and a third step of pressing each lead from obliquely above to bend the lead in such a manner that a tip portion of the lead having the first and second bent portions is located at a bottom portion of the resin mold section. Since the lead is pressed from obliquely above and bent in such a manner that a tip portion of the lead having the first and second bent portions is located at a bottom portion of the resin mold section, an angle xcex1 in FIG. 6B is secured and the tip of the lead is accurately bent toward a bottom portion of the electronic part.
According to another aspect of the invention, the first bent portion is formed while the lead is simultaneously inclined upward. By doing so, the first bent portion has an acute bending angle to allow the tip of the lead to be accurately bent toward the bottom portion of the electronic parts.
According to another aspect of the invention, the first bent portion is formed while the V-shaped groove is simultaneously formed near a root of the lead. When the root of the lead is bent, the bending is easy because the V-shaped groove has been formed in this position. In addition, the occurrence of a crevice can be prevented.
According to another aspect of the invention, the first bent portion is formed between the tip portion and an intermediate portion of the lead. When a neighborhood of the first bent portion is pressed downward to form the second bent portion, the pressed portion of the lead is sufficiently distant from a neighborhood of the root, so that a bending stress concentrates in the V-shaped groove formed at the first step, thereby allowing the lead to be accurately bent.
According to another aspect of the invention, the second bent portion is formed near the root of the lead. As such, the lead can be bent along a shape of the resin mold section of the electronic part.
In a method for manufacturing electronic parts according to another aspect of the present invention, each electronic part includes a resin mold section with a built-in electronic element and leads projecting therefrom. The method comprises the steps of bending a lead upward in a neighborhood of a root thereof while simultaneously bending a first portion of the lead to form a first bent portion, and pressing the lead from obliquely above to bend the lead with the first bent portion so that a tip of the lead is located at a bottom portion of the resin mold section.
According to another aspect of the invention, a neighborhood of a root of the lead is bent upward while a V-shaped groove is simultaneously formed near the root of the lead. The first bent portion has an acute bending angle to allow a tip of the lead to be accurately bent toward a bottom portion of the electronic part. When a neighborhood of the root of the lead is bent again, the bending is easy because the V-shaped groove has been formed in this position. In addition, the occurrence of a crevice can be prevented.
According to another aspect of the invention, the electronic part is a quartz oscillator. Thus, a thin quartz oscillator can be implemented.
An apparatus for manufacturing at least one electronic part according to another aspect of the present invention is also provided. Each electronic part comprises a resin mold section with a built-in electronic element and leads projecting therefrom. The apparatus comprises a first bending punch for bending a first portion of each lead to form a first bent portion, a first bending die formed in a fashion corresponding to the first bending punch, a second bending punch for bending a neighborhood of a root of the lead, a second bending die located in a fashion corresponding to the second bending punch, a cam driver for further bending the bent portion near the root, and a third bending punch formed in a fashion corresponding to the cam driver, the first bending die having a projection formed thereon to form a V-shaped groove near the root of the lead. Since the projection is formed on the first bending die for forming the first bent portion, the V-shaped groove can be formed near the root of the lead.
According to another aspect of the invention, a vertex of the projection has an angle set between 60xc2x0 and 90xc2x0. As such, the V-shaped groove formed in the lead is sized so that it is not closed even after a neighborhood of the root of the lead has been bent, thereby enabling accurate bending when further bending the bent portion near the root.
In accordance with another aspect of the present invention, an apparatus for manufacturing at least one electronic part is provided. Each electronic part comprises a resin mold section with a built-in electronic element and leads projecting therefrom. The apparatus comprises a first bending punch for bending a first portion of each of the leads to form a first bent portion, a first bending die formed in a fashion corresponding to the first bending punch, a second bending punch for bending a second portion of the lead, which is different from the first portion, to form a second bent portion, a second bending die located in a fashion corresponding to the second bending punch, and a third bending punch for pressing the lead from obliquely above to bend it in such a manner that a tip portion of the lead having the first and second bent portions is located at a bottom portion of the resin mold section. Since the third bending punch is installed on an upper die, the apparatus is not substantially affected by scraps. Additionally, by setting an angle of an inner wall of the bending punch taking the amount of spring back of the lead into consideration, accurate bending is secured.
According to another aspect of the invention, the first bending punch and the first bending die are arranged so that the first bent portion is formed between the tip portion and an intermediate portion of the lead. Thereby, the first bent portion is formed.
According to another aspect of the invention, the second bending punch and the second bending die are arranged so as to form the second bent portion near a root of the lead. Thereby, the second bent portion is formed.
According to another aspect of the invention, the third bending punch has a curved surface portion brought in contact with the lead section, thereby avoiding the scratch on the lead surface.
According to another aspect of the invention, the first bending die has a projection formed therein for forming a V-shaped groove near the root of the lead. The projection of the first bending die forms the V-shaped groove.
According to another aspect of the invention, the projection has a height set between about one-third and about one-half of the thickness of the lead formed in the electronic parts, thereby retaining a strength of the V-shaped groove in the lead.
According to another aspect of the invention, the projection is formed so that its vertex has an angle between 60xc2x0 and 90xc2x0. Thus, the groove in the lead is sized so that it is not closed even after the second bending portion has been formed, thereby enabling accurate bending when bending a tip of the lead toward a bottom side of the electronic part.
According to another aspect of the invention, the first and second bending dies are formed to contact at least partly with a neighborhood of the root of the lead. The bending dies are formed to contact with the neighborhood of the root of the lead, thereby allowing the lead to be stably bent.
According to another aspect of the invention, the manufacturing apparatus further comprises a cam driver for driving the third bending punch. Since the cam driver is mounted on an upper mold, the apparatus is hardly affected by scraps.
According to another aspect of the invention, the third bending punch has a surface inclined at a predetermined angle with respect to a vertical direction. This enables a sliding surface of the bending punch to be set wide, replacements of parts caused by biased abrasion is less frequently required, resulting in easy maintenance. In addition, since this structure requires no lever shaft contrary to the prior art, no part has an extremely short life time, also reducing the frequency of maintenance operations.
According to another aspect of the invention, the third bending punch is provided in a stripper plate via a spring member.
According to another aspect of the invention, each of the bending punches and each of the bending dies are formed, so as to bend leads formed in a major axis direction of the electronic part. The present invention is thus applicable to electronic parts having leads formed in the major axis direction.
According to another aspect of the invention, each of the bending punches and each of the bending dies are formed so as to bend leads formed in a minor axis direction of the electronic part. The present invention is thus applicable to electronic parts having leads formed in the minor axis direction.